The present invention relates generally to an infrared radiator unit, and more particularly to an infrared radiator unit for infrared analyzers.
Infrared radiator units of this type are used in infrared analyzers and are electrically heated to approximately 1000K, so that the energy radiated by them is in the infrared portion of the spectrum.
When such units are used in infrared analyzers for measuring purposes, specific requirements are made of them with respect, inter alia, to the direction of the infrared radiation and the constancy of the emitted radiation, as well as with respect to the energy requirements of the source.
It is known that a particularly high effectiveness of the radiation utilized for measuring purposes can be obtained, if the infrared radiation which leaves the radiator unit issues in axially parallel condition, because this assures that the largest part of the radiation will enter axially parallel into the measuring or reference receptacle, rather than entering into it at an angle to impinge upon its side walls and become partly absorbed therein. To obtain this direction of the radiation it is known in the prior art to configurate the reflecting surface of the reflector of the unit as a paraboloid. However, the energy sources used in the art are not point sources but have an elongated configuration, so that a purely paraboloid-shaped reflecting surface does not adequately condense the radiation into a direct beam.
Another prior-art difficulty has been the very substantial influence of heat losses via the mountings of the energy source and the unit per se, upon the constancy of the radiation intensity. The better thermal conductivity there is between the energy source, the mount for the energy source and the housing, the more substantially the temperature of the energy source will be influenced by the ambient temperature, and this in turn leads to a wavelength shift in the major portion of the emitted radiation, so that the intensity of radiation is not constant.
Furthermore, it is desired that such infrared radiating units should require as little energy as possible for the operation, a condition which is particularly important if such units are employed in battery-operated infrared analyzers where the available battery energy is strictly limited.
Finally, another problem that has not been solved in the art is the mechanical stability of the mounting arrangement for the radiant energy source. If the source is shifted in any way in its position relative to the optical axis of the analyzer, by mechanical vibrations or the like, then the symmetry of the arrangement is disturbed and errors in measurement can and will occur.